The current invention deals with improvements relating to mobile communication standards, in particular, with improving the so called “last mile” between a radio base station and a radio access network or a portion thereof, avoiding unwanted or noticeable effects for the end users.
In today's circuit switched telecommunications networks payload traffic and signaling are handled in different logical networks. Signaling traffic pertains to the signaling plane while the payload traffic is transported in the user plane.
The user plane of a call between two radio terminals, such as GSM terminals, is routed from a Base Station Subsystem (BSS) network to a core network and back to a BSS network.
Such a network consists of several Interfaces, some of them are of particular interest in the following.
The A-Interface relates to the Interface between a Mobile Switching Center (MSC) and a Base Station Subsystem (BSS) controlled by the Base Station Controller (BSC). The Abis Interface relates to the Interface between a Base Station Controller (BSC) and a Base Station Transceiver (BTS). The Radio Interface relates to the Interface between a Base Station Transceiver (BTS) and a Mobile Station (MS). These terms refer to GSM like networks.
These interfaces have correspondences in an UMTS like network. There the correspondence to the A Interface is the Iu Interface between a Mobile Switching Center (MSC) and a Radio Network Controller (RNC). The correspondence to the Abis Interface is the Iub Interface between a Radio Network Controller (RNC) a NodeB and the correspondence to the Radio Interface is again the Radio Interface between NodeB and a User Equipment (UE).
In today's networks, the radio and Abis-Interface-resources and the A-Interface-resources are quite early in the call setup phase allocated to ensure their availability; this procedure is therefore often referenced as “early assignment”.
FIG. 1a and FIG. 1b shows a typical exemplary Call Flow for an early assignment.
There a UTRAN-based call with some typical timing values is shown.
After User 1 has decided to select a number in step 1, the number corresponding to User Equipment 2, and presses in step 2 the dial button, the User Equipment UE1 accesses B1 in a step 3 and in a step 4 the UE1 submits a Service Request towards MSC1. From pressing dial until now, around 1 second has passed.
Now the MSC1 asks in a step 5 the UE1 for authentication which is provided in step 6. Thereafter signaling is exchanged pertaining to the UE1 capabilities in steps 7 and 8. In the meantime, the MSC has interrogated an HLR for routing data of UE2 in the background.
Thereafter the MSC1 sends an IAM message with a codec (list) towards MSC2 in step 9.
MSC2 in turn instructs RNC2 to page the User Equipment 2 which is done in steps 10 and 11. The response is received in steps 12 and 13.
Now the MSC2 asks in a step 14 the UE2 for authentication which is provided in step 15. Thereafter signaling is exchanged pertaining to the UE2 capabilities in steps 16 and 17. Step 17 is displayed on FIG. 1a as last step and again on FIG. 1b as first step.
After having received capabilities in step 17, MSC 2 sends the selected codec towards MGW 2 in step 18 and receives back the address in step 19.
The MSC sends the selected codec and the address to MSC in step 20. The selected codec and the address is than send to MGW 1 in step 21 and acknowledged in step 22.
Thereafter, in step 23 the UE 1 is informed via RAB Assignment of the selected originating RAN Circuit which is acknowledged in step 24.
Shortly thereafter also the second Radio- and Iub-(Abis-)-legs of the User Plane are assigned towards the User 2 (the called user).
MSC 1 sends in step 25 a continuity message towards MSC 2 which in turn sends a corresponding RAB Assignment with the selected terminating RAN circuit towards UE 2 in step 26. The UE 2 acknowledges said message in step 27.
Now the User 2 hears a ringing in step 28 while the UE 2 reports towards the MSC 2 that it is Alerting.
From pressing the dial button until now around 5 seconds have passed.
A first learning thereof is that it takes about 5 seconds after User 1 (the calling user) pressed the “dial” button that the first Radio- and Iub-(Abis)-legs of the User Plane are assigned.
Now the MSC 2 reports towards MSC 1 in step 29 that it is Alerting while the MSC 1 instructs in step 30 the MGW2 to generate ring back tone.
MSC 1 on receiving Alerting message from MSC 1 in step 29 forwards said message towards the UE1, the UE 1 in turn shows alerting in step 31.
MGW 2 on receiving the generate ring back tone in step 30 generates the ring back tone in step 32 and provides the ring back tone towards the UE 1. The User 1 will hear in step 33 the generated ring back tone.
Now after some ring tones, another couple of seconds have passed, the User 2 accepts the call in a step 34. The UE 2 reports Connect towards the MSC 2 in step 35 which in turn instructs the MGW 2 to stop ring back tone and to connect to the UE 2 in step 36. In the meantime the MSC 2 also reports Connect towards MSC 1 in step 37.
MSC 1 in turn instructs MGW 1 in step 38 to connect in both directions and in another step 39 the Connect report is forwarded to the UE 1 which shows the connected state in a step 40 towards the User 1.
A second learning is that it takes another couple of seconds until the User 2 accepts a call if the User 2 accepts the call at all.
This time, where the called mobile is ringing is a waste of expensive resources. Often the called user is not at all accepting the call and the ringing phase may be very long and totally without success and without income for the operator at the end.
Hence, resources are assigned even though they may not be used for some time or not at all. These resources are then allocated and not available for other calls, although no speech communication is possible, until User 2 (the called user) accepts the call.
The problem becomes even worse in cases where the Iub-, Iu- (Abis- and A-) resources are routed via expensive or capacity limited links, such as satellite links, this leads to an inefficient usage of these expensive resources in an early stage.